An object is to accurately calculate an index indicating a probability of an event occurring to a patient in the future. A mortality risk calculation unit acquires a heart/mediastinum ratio (H/M ratio), obtained by administering a heart function diagnostic medicine to a first subject, from subject data stored in a subject data storage unit, and calculates an index indicating a probability of a predetermined event occurring to the first subject by substituting the H/M ratio acquired from the subject data storage unit into a function defined in accordance with a history of occurrences of the predetermined event to a plurality of second subjects.
